Aircraft: EMB ERJ 145 ER/LR
Phase of flight: Taxi
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Passenger Misconduct

There was a taxi delay heading out to the runway as usual. After about 20 minutes of taxiing; I completed the before takeoff checks which includes a PA requesting the flight attendants to 'please be seated for departure.' We were number 2 for takeoff when suddenly we received a cascade of various EICAS messages. These included WINDSHEAR INOP; GPWS INOP; TERRAIN FAIL; E1 SHORT DISP; and RAD ALT 1 FAIL. We advised ATC that we needed to leave the queue and taxi somewhere to work on the problem. The Pilot in Command then contacted Maintenance and worked with them by phone on troubleshooting. In the meantime I advised the flight attendants that we were working on a problem and that we weren't sure yet if we'd need to return to the gate or not. I remained on Comm 1 in order to monitor ATC while the pilot in command was on the phone with Maintenance. It took only about 10 minutes to troubleshoot the issue. By this time it was around 30-35 minutes since we blocked out.After being unable to resolve the issue; Maintenance advised us to return to the gate. The Pilot in Command then made two separate PA calls to the passengers. The first PA call was made immediately after Maintenance told us to return to the gate. The second PA call was made a few minutes later as we taxied back to the gate. The Pilot in Command apologized to the passengers for the problem; explained that we tried to resolve it; but unfortunately needed to return to the gate for further inspection. Due to the heavy congestion on the airport; it took a while to return to the gate. We blocked in about 1 hour after we first blocked out. By this point everything seemed routine.However; upon arriving at the gate; two passengers became extremely irate. One in particular was the passenger sat in seat 1A. This passenger said he had 'two million miles' and promised 'to report the crew to the airline CEO for not communicating any information to the passengers.' They also stated that they did not appreciate 'waiting for over an hour on the airplane with no information'. We only knew of the problem for 10 minutes before making the decision to return to the gate and making our first return to gate PA call.This passenger's aggressive behavior rapidly became very erratic and it visibly upset our flight attendants. The anger that this passenger was expressing did not seem proportionate to the issue at hand. The Pilot in Command then got out from the cockpit to talk to the passenger personally in an attempt to deescalate the situation. Unfortunately; there was nothing the Pilot in Command could do to calm this passenger down. The gate agent eventually came down the jet bridge and we the crew remained on board the airplane for our own personal security. At first we were worried that the Pilot in Command's PA calls were not being heard; hence why the passengers felt they were left in the dark. But both the flight attendants as well as a deadheading pilot confirmed that there were indeed PA calls made that were loud and clear. We believe that the passengers were under the mistaken impression that the delay we experienced taxiing to the runway was the result of the maintenance issue; whereas it was due to normal delays at Newark.After deplaning the gate agent advised us that this irate passenger 'had left and was nowhere to be seen.' It was assumed he left to catch another flight. Because of this information we did not feel it was necessary to advise the gate agent to deny re-boarding of this passenger. However; after Maintenance resolved the issues and we began re-boarding. We were surprised to see that the same passenger was back and ready to take his seat. He was the first one to board no less. We then paused boarding to discuss this situation with both the flight attendants and the gate agent. Our primary concern was to ensure that the flight attendants felt safe. Although she was initially hesitant having this passenger on board she ultimately did agree that she would becomfortable with this passenger on board. The Pilot in Command then had a word with this passenger before he took his seat. The passenger was noticeably more calm; which somewhat assured us that he would not be disruptive again. We assured the flight attendants that if this passenger were to become disruptive after the main door was closed that we would promptly return to the gate. Fortunately; we completed an uneventful flight with no further disruptions by this passenger. In the future I think we should be more explicit with the gate agent when a passenger should be denied boarding; even if it's assumed or implied that said passenger has left. ERJ First Officer reported receiving multiple EICAS messages prior to departure that resulted in a return to the gate; a maintenance action; and a passenger becoming unruly.